Setsuna was first seen with Taisuke,Hikari and Nanami where she says that Makoto is about to cry and make a V hand sign in front of him while he tries to denied it,then watches Makoto and Sekai's "couple skinship" relationship until the teacher arrives,afterwards she is seen with Sekai and her friends during the P.E class together along the girl's locker room.After Class Setsuna leaves Sekai and Makoto in the class with Nanami and Hikari.
Next day Setsuna invites Sekai to have lunch with her after the latter pushes Makoto and Kotonoha to have a private time together at the rooftop,After class due to being a class representative she joins in the conference meeting with the other representative (Kotonoha included).

Someday Setsuna along with Nanami and Hikari once more joins to have lunch again with Sekai,at the canteen Setsuna was quietly eating her lunch until she witness that Sekai was overprotective over her phone and quietly watches Sekai leaving.After class Setsuna asks Sekai about what happened during lunch which Sekai apologise to her about making her worried until Kotonoha along with Makoto arrives who offers to go home with them which Sekai agrees here Setsuna asks Sekai about her acquaintance to her which she tells Setsuna that she knows her through Makoto,then tells her that she knows her in the student council.As they walked home Setsuna watches Makoto pulls Sekai who is absent-mindedly crosses the road while the truck passes by nearly hitting her and causing her phone to drop in the process,

Setsuna had looked on Sekai's phone

Setsuna picks up Sekai's phone and glamours on her wallpaper which is presumably Makoto himself,here Setsuna confronts Sekai and shows her that she had looked on her phone then Sekai tells him about it,her reaction to this is unknown.

Summer Vacation has arrived and Setsuna joins with Sekai and her friends along with Makoto to the beach,overtime Nanami declared a watermelon smashing challenge and Setuna teams up with Nanami which they lost the game to Makoto and Sekai.She spends time having fun on the beach until sunset arrives.

At the day of the summer festival Setsuna joins to attend the festival with Sekai,Nanami,Hikari,and Taisuke until they found Makoto and Kotonoha who are also attending the festival as well and Sekai manages to let them join as well,while they enjoy the festival Setsuna easily carved a phoenix using a clay startling both Taisuke and Makoto.

School time arrives and Sekai tells her that she won't coming to school today,when Makoto asked Setsuna about her absence she tells him to visit her which he accepted.The school festival arrives and the class from Setsuna was where maid cafe here when Hikari forces Makoto and Sekai to have time together Setsuna was visibly smiling.

At some day Setsuna learns that Makoto was hospitalized and visits him with her friends,when Nanami mention Sekai and asked her whereabouts she told her that Sekai had to finished some "errands" until the latter arrives and leaves them both unknowingly that soon Sekai will kill Makoto.